Databases Reference
In-Depth Information
Table2.1
A Set of Unit Price Data for Items
Sold at a Branch of
AllElectronics
Unitprice Countof
(
$
)
itemssold
40
275
43
300
47
250
74
360
75
515
78
540
115
320
117
270
120
350
120
110
100
90
80
70
60
50
40
Q
3
Median
Q
1
40
50
60
70 80
Branch 1 (unit price $)
90
100
110
120
Figure2.5
A q-q plot for unit price data from two
AllElectronics
branches.
data, which is plotted against the
.
i
0.5
/=
M
quantile of the
x
data. This computation
typically involves interpolation.
Example2.14
Quantile-quantile plot.
Figure 2.5 shows a quantile-quantile plot for
unit price
data of
items sold at two branches of
AllElectronics
during a given time period. Each point cor-
responds to the same quantile for each data set and shows the unit price of items sold at
branch 1 versus branch 2 for that quantile. (To aid in comparison, the straight line rep-
resents the case where, for each given quantile, the unit price at each branch is the same.
The darker points correspond to the data for
Q
1
, the median, and
Q
3
, respectively.)
We see, for example, that at
Q
1
, the unit price of items sold at branch 1 was slightly
less than that at branch 2. In other words, 25% of items sold at branch 1 were less than or
